1. Field of the Invention
The present invention relates generally to an apparatus and process for cleaning gold plated contact surfaces of printed circuit boards and, more particularly, to an apparatus and process for removing contaminants from gold plated contact surfaces by using a grindstone in contact with the gold plated contact surfaces.
2. Description of the Prior Art
Typically, on printed circuit boards various components (e.g. resistors, capacitors, inductors, integrated circuits and the like) are mounted and soldered. The components are electrically connected to each other to function via pre-patterned copper wiring traces formed on the surfaces of printed circuit boards. Surface mounting technology components and printed board assembly components are mounted upon printed circuit board assemblies. After the surface mount technology components are mounted and soldered on the surface of the printed circuit board, the printed board assembly components are inserted through the holes on the printed circuit board and the assembly is introduced into a soldering machine. Flux is applied to the printed circuit board in a flux bath, the board is preheated in a heater, the solder ports of the printed circuit board are soldered, and the printed circuit board is then cooled upon completion of the soldering.
Printed circuit boards serve as main boards or as expansion boards in electronic appliances such as personal computers. Usually, the expansion boards are adapted for expanding the functions of the personal computers and have gold plated contact surfaces that enable the board to be inserted into the slots on a main board and while forming electrical connections allowing the functionally extended boards to communicate via signals exchanged with the main board. These gold plated contact surfaces are contaminated by the flux applied however, and the residue and other dirt stain the gold plated contact surfaces due to oxidized gas generated during soldering. Such contaminants on the gold plated contact surfaces exhibit poor electrical connection with the slots and connectors.
Other efforts that used grinding of circuit boards included the Biased Grinding Assembly of T. F. Dawson, et alii, U.S. Pat. No. 4,748,773, and the Sample Holder For Use In The Grinding Or Polishing Of Samples of J. T. Voss, et alii, U.S. Pat. No. 4,895,033. Other processes such as the Selectively Plating Electrically Conductive Pin by Peter Tsuk, U.S. Pat. No. 5,190,486, seek to avoid leading residue or contaminants on gold plated contact regions by the expedient of a partially cured, aqueous stripping system. Relatively recent efforts such as the shot blasting technique of Nobuhiko Tada, et alii, found in U.S. Pat. No. 5,548,890 entitled Lead Frame Processing Method, eject minute particulates that collide with the circuit board; this technique relies upon the kinetic energy of the particulates to remove spatters and dross deposited during manufacture of the circuit board.
Customarily, the gold plated contact surfaces formed on a circuit board are manually erased with an eraser after the soldering process to remove the various contaminants; however the contaminants caused by the oxidized gas can be erased with an eraser while the flux can not be removed effectively in the same manner and the presence of the human operator diminishes production efficiency. Moreover, it is hard to uniformly remove the contaminants and the operating conditions become worse due to the creation of waste particles from the eraser.